Targeting apoptotic anticancer response with natural glucosinolates from cell suspension culture of Lepidium sativum

Finding natural products with anticancer activity is an effective strategy to fight this disease. In this respect, Lepidium sativum or garden cress (family Brassicaceae) has been widely used worldwide for its wide therapeutic application, including anticancer and chemoprotective agents. Plant tissue culture techniques hold great promise for natural product enhancement without any climatic boundaries. In this study, glucosinolates and petroleum ether fractions were isolated from in vitro cell cultures and used against different carcinoma cell lines to investigate their anticancer potential.

In this study, callus cultures from leaf and root explants were initiated, cell suspension cultures were established, and cell growth and viability profiles were characterized. Different amino acids were added as precursors to the cell suspension cultures to enhance glucosinolates accumulation. Gas chromatography-mass spectrometric analysis (GC-MS) of glucosinolates and petroleum ether fractions was performed, and all fractions were tested against different carcinoma cell lines.

The findings clarified that the maximum callus initiation percentage was obtained in the medium containing 1.0 mg/l 2,4-dichlorophenoxy acetic acid (2,4-D) + 1.0 mg/l kinetin (Kin) (C1). The viable cell number of cell suspension cultures from leaves and roots increased until it reached the maximum values on day 15. Adding tyrosine and methionine to the cell suspension cultures was the most influential and recorded high glucosinolate percentages. 1H-Cyclopenta (b) pyridine-3-carbonitrile-4,5,6,7-tetrahydro-2-methylthio-4-spirocyclohexane was the main glucosinolate compound found in tyrosine-treated leaf suspension (GLT). Fifteen compounds were detected in the petroleum ether fraction in both cell suspensions initiated from the leaf and root (OL and OR). The major compounds were benzene-1,3,5-trimethyl (12.99%) in root cell suspension (OR), and benzene-2-ethyl-1,4-dimethyl (10.66%) in leaf cell suspension (OL). All glucosinolate extracts demonstrated significant anticancer activity against the prostate (PC3), lung (A-549), colorectal (caco2), and liver (HepG2) cell lines. Glucosinolates extracted from leaf cell suspension (GL) were the most active on the hepatocellular carcinoma cell line (HepG2) among all remaining glucosinolate extracts. Treated hepatocellular carcinoma with an IC₅₀ of GL extract (47.5 ug/ml) upregulates pro-apoptotic BAX and downregulates anti-apoptotic BCL2, which disrupts the BAX/BCL2 ratio, leading to activation of caspase 3 inside treated HepG2 cells.

The anticancer action of the GL extract was validated by the cell cycle study of its glucosinolates, which successfully promoted apoptosis and reduced hepatocellular growth by causing S-phase arrest.